In a field of strip heaters or line heaters, a coil hearer constituted by a nichrome filament and a lamp heater, such as an infrared ray lamp, which is shaped into a long straight line are conventionally used.
The coil heater, however, has a drawback that it is difficult to reduce the thickness of the coil heater. Thus, the coil heater is not suitable for the use in a narrow place. Further, the coil heater is weak when subjected to mechanical stress.
The lamp heater also has the drawback that it is difficult to reduce the thickness of the lamp heater. Thus, the lamp heater is nor suitable for the use in a narrow place. Further, the lamp heater does not quickly reach a stable operation state when power is applied thereto.